Metal die casting and method of degating

ABSTRACT

Metal die casting apparatus including three abutting plates of which the outside plates are movable relative to the center plate. The casting is formed in one plate and the gate for leading the molten metal to the casting is formed in the other plates. After forming the casting, the gate is broken off and ejected by movement of one end plate. The casting is then ejected by movement of the other end plate. The novel plate apparatus and the method of degating provides a pinhole break-off point so that trimming of the cast part is unnecessary.

UnitedStates Patent Hannes May 6, 1975 [54] METAL DIE CASTING AND METHOD OF 3,283,373 11/1966 Kiefer et a1. 164/262 DEGATING 3,327,355 6/1967 Carlin 249/66 3,627,023 12/1971 Clark et a1. 164/264 [75] Inventor: Karl Hannes, White Plains, NY.

[73] Assignee: Coats & Clark, Inc., New York, Primary Examiner Robert Baldwin Assistant ExaminerV. K. Rising [22] Filed: Dec. 3, 1973 [21] Appl. No.: 421,154

[57] ABSTRACT Related US. Application Data [62] Division OfSer. No. 274,910, July 25, 1972, Pat. No. Metal die casting apparatus i i g three b i g 3,854,521. plates of which the outside plates are movable relative to the center plate. The casting is formed in one plate [52] US. Cl. 164/113; 164/70; 164/262; and the gate for leading the molten metal to the cast- 164/ 131; 164/347; 164/404; 249/66; 249/67 ing is formed in the other plates. After forming the [51] Int. Cl B22d 27/10 casting, the gate is broken off and ejected by move- [58] Field of Search 164/113, 69, 70, 303, 347, ment of one end plate. The casting is then ejected by 164/262, 264, 265, 131, 344, 404, 401, 305, movement of the other end plate. The novel plate ap- 304, 312, 313, 314, 320, 309; 249/67, 68, paratus and the method of degating provides a pinhole 66, 161; 425/444, 441 break-off point so that trimming of the cast part is unnecessary. [56] References Cited UNITED STATES PATENTS Shaw 425/444 4 Claims, 6 Drawing Figures METAL DIE CASTING AND METHOD OF DEGATING This is a division of application Ser. No. 274,910, filed July 25, 1972, now US. Pat. No. 3,854,521.

BROAD STATEMENT OF INVENTION The present invention relates to metal die casting apparatus and a method of casting and degating, and is particularly concerned with movable die plates providing a pinhole break-off gate with respect to the cast part.

DESCRIPTION OF THE PRIOR ART In the prior art the casting of metal parts is effected by injecting the molten metal from a nozzle into a runner or gate that leads to the recess for forming the cast part. After casting, the part and the gate form an integral unit, and the gate has to be broken off before the cast part is further treated. The gate can be broken off by various procedures, such as a special tool or tumbling, but this results in a rough surface that must be later smoothed, trimmed or otherwise treated. Accordingly, it would be desirable in metal casting to be able to break off the gate without the necessity for the trimming or tumbling operation.

DESCRIPTION OF THE INVENTION The present invention provides a metal die casting apparatus including three abutting die plates of which the outer two are movable for separation of the attached gate from the cast part.

In the present invention metal die casting apparatus is provided which includes three abutting plates with the casting formed in one outer plate and the gate in the other two plates, separation of the gate from the cast part being effected by movement of one outer plate.

A further provision of the present invention is a metal die casting apparatus having three abutting plates in which the cast part is formed in one plate and the other two plates are configured to provide a conical gate with a break-off tip.

There is further provided by the present invention a metal die casting apparatus having three abutting plates in which the cast part and attached gate are formed to be separately degated and ejected by pins sliding through the outside plates.

There is also provided in the present invention a method of metal die casting in which plates are positioned in abutting relationship within which a cast part and attached gate are formed, the part and gate being separately ejected by movement of the outer plates.

A further provision of the present invention is a method of metal die casting in which abutting plates having a cast part and attached gate formed therein are sequentially moved relative to each other, and the plates include pins that slide therein to separately eject the cast part and the gate.

In a preferred embodiment of the die casting apparatus three plates are placed in abutting position so that molten metal can be injected therein. One of the outside plates includes a recess in which the part is cast, and the center plate includes a through opening while the other outside plate includes another recess. The opening and the other recess form the gate during casting. Each of the outside die plates is movable relative to the center plate. The opening in the center plate is conically shaped and tapers to a small opening at the end abutting the recess where the part is cast. After the molten metal solidifies, the outside plate including part of the gate is moved away from the center plate thereby breaking off the gate from the part. A pin is slidably mounted within this movable plate and projects therefrom so that when it strikes a fixed part of the machine, the gate which has been broken off from the cast part is then ejected by the sliding ejection pin. It is to be noted that the gate is conically formed tapering to its smallest size where it contacts the cast part so that breakage is easily effected at this contact point. Moreover, the part of the gate in the first movable plate is larger in size than the rest of the gate to insure that the breakage occurs at the cast part. The other outside plate including the cast part is then moved relative to the center plate and includes a sliding ejection pin that ejects the cast part when it strikes a fixed part of the apparatus. This sequential ejection of the gate and cast part provides a pinhole break-off point and ejection of the part whereby trimming is unnecessary.

A further provision of the present invention is a method of metal die casting wherein three die plates are first placed in abutting relation so that molten metal injected therein will form a cast part in one outside plate and an attached gate that is partly within the inside plate and partly in the other outside plate, the gate within the center plate being conically shaped and tapering toward the cast part. The outer plate including part of the gate is then moved away from the center plate for degating causing the gate to break off from the cast part at the small conical tip, and a sliding ejection pin then knocks the gate out of the die plate. Subsequently, the other outside die plate including the cast part is moved relative to the center plate and a sliding pin mounted therein operated to eject the cast part from the die plate.

The nature of the present invention will become more clearly apparent and better understood from the following description and accompanying drawings in which:

FIG. 1 is a front elevational view illustrating a die cast element and its attached gate as formed by a prior art procedure;

FIG. 2 is a schematic view, partly in section, showing the die plates of the present invention in abutting relation;

FIG. 3 is a view similar to FIG. 2 showing a displaced movement of one of the die plates;

FIG. 4 is a view similar to FIG. 3 showing a further step in the operation of the present invention;

FIG. 5 is a view similar to FIG. 3 showing a displacement of the other outside die plate; and

FIG. 6 is a view of the gate formed in the present invention.

In FIG. 1 a cast part 10 is shown which may be a metal slider element of a zipper. In the prior art when this slider is die cast of metal, the molten metal is introduced to a runner or gate 12 which has a fan-shaped part 14 where the metal flows into the mold or recess forming cast part 10. After solidification, cast part 10 is thereby attached to gate 12, and it is necessary to degate part 10. This has been done in the prior art by a special tool or by tumbling the assembled part and attached gate, but it is then necessary to trim part 10 since the surface is rough where fan-shaped part 14 breaks off.

In the present invention as shown in FIGS. 2-5 a novel arrangement of die plates and method of degating is presented resulting in an improved break-off arrangement so that trimming is no longer necessary. It is understood that the die casting apparatus would include the usual support with a power drive and cam actuation to provide for the movement of the parts. Since such elements are all conventional, they are not shown for purposesof clarity, and only the novel die plates and associated features are illustrated.

Three die plates constitute the primary novel feature and includes a center plate 16 which is substantially fixed with respect to the apparatus and outside plates 18 and 20 which are relatively movable with respect to center plate 16. In FIG. 2 the die plates are shown in the normal casting position in abutting relation with the recesses and opening described hereinafter ready to receive for the injection of the molten metal, such as zinc. Outside plate 20 is shown as a first die plate and includes a first recess 22 which is formed on the side abutting center plate 16 and in which the cast part is formed. A sliding ejection pin 24 is mounted within plate 20 and located so that it can slide into recess 22.

Center plate 16 includes a through opening 26 which is generally conically shaped. One end includes a small opening 28 in alignment with the approximate center of recess 22 and enlarging therefrom at a predetermined conical angle for approximately one-third of the thickness of plate 16. Opening 28 continues to enlarge therefrom at a smaller angle and terminates in enlarged opening 30 at the other end of plate 16 where it abuts plate 18.

Outside plate 18 includes a second recess 32 having a special configuration and generally aligned with opening 30. The configuration of recess 32 has a transverse dimension parallel to the surface of plate 18 which is greater than the corresponding transverse dimension of opening 30. As shown in FIG. 2 a top surface of recess 32 extends generally perpendicular to the surface and continues on to form a concave curved portion 34 of the plate to connect with a base surface 36. It is understood that concave curve 34 extends around the periphery of recess 32 which is generally circular in shape, and a convex curved portion 38 of the plate 18 connects the lower part of base curve 34 with the outer abutting edge as shown in FIG. 2. This convex curvature 38 is an important feature of the invention, and although the exact curvature is not critical, it must be of a convex nature as will be explained hereinafter.

As shown in phantom at the top of FIG. 2, a nozzle 40 injects molten metal into a conduit 41 thereby forming a runner 42 (see FIG. 4) so that the molten metal flows into opening 26 and recesses 22 and 32.

As seen in FIG. 3, a cast part 44 has been formed in recess 22. An attached gate 46 was formed by the molten metal with part of the gate in inner plate 16 and part of the gate in outer plate 18. Originally cast part 44 is formed integral with gate 46, but FIG. 3 shows a step in the breaking off of gate 46. As a feature of the present invention, the outer plate 18 is first moved perpendicular to the surface of plate 16 and away from fixed plate 16 to the position shown in FIG. 3. Since the attaching connection between part 44 and gate 46 is smaller than any other part of gate 46, breakoff occurs at the abutment of plates 16 and 20. This can be considered a pinhole break-off point since the opening 28 is sufficiently small so that the break-off leaves a small mark in the nature of a pinhole that does not require trimming as in the prior art. In fact, it is possible to design the location of the opening 28 so that the attachment of cast part 44 and gate 46 occurs at a recessed area, the pinhole marking being scarcely visible and causing no problem as to any rough surface.

Plate 18 includes a pin 33 slidable therein that is positioned in the casting position shown in FIG. 2 to have one end abutting recess 32. In FIG. 3 plate 18 has been moved to the right and it will be noted that ejection pin 33 is approaching a fixed part 48 of the apparatus. Pin 33 is mounted so that it can slide within gate 18, and in FIG. 4 pin 33 is seen to strike a fixed part 48 whereby it is slid into recess 32 to eject gate 46. In FIG. 4 gate 46 is in the process of being ejected to fall into the space between plates 16 and 18.

In FIG. 5 the next step of the operation is shown where outer plate 20 is moved to the left relative to fixed center plate 16. An ejection pin 24 is mounted to slide within plate 20 in the same manner as pin 33 is mounted in plate 16. Accordingly, when pin 24 strikes a fixed part 50 of the apparatus, the end of pin 24 slides into recess 22 so that die cast part 44 is ejected therefrom and falls into the space between plates 16 and 20.

From the above description it is clear that a sequence of steps provides the novel method features of the invention, and the plate arrangement with the novel configuration thereof provides the gate with the pinhole break-off point. The gate itself is formed in a particular configuration as shown most clearly in FIG. 6 so that the movement of die plate 18 allows the desired break off and particular ejection to take place.

As mentioned previously part of gate 46 is formed in the center die plate 16 and part of the gate is formed in movable outer plate 18. Since recess 26 has larger end 30 opposite smaller end 28 which abuts recess 22, gate 46 is formed with a generally conical shape having a tip 52 of smallest size as compared to the rest of gate 46 and therefore the weakest strength to insure that breakage will occur at that tip point when die plate 18 is moved away from die plate 16. Since recess 32 has a larger transverse dimension, an undercut portion 54 is formed as part of gate 46. An intermediate area 56 between end 52 and undercut portion 54 provides a change in the angular conical form. A greater angle is provided between end 52 and intermediate area 56, and a smaller conical angle is provided from area 56 to undercut portion 54.

A critical feature of the invention is a concave area 58 in the gate that is formed due to convex surface 38 in die plate 18. The large or head area of gate 46 includes rounded surface 60 formed by the curved surface 34.

Since the concave area 58 is held in plate 18, and since point 52 is of such small size, it is clear that movement of die plate 18 to the right (FIG. 3) will cause gate 46 to be broken off at point 52 and be retained within die plate 18 as shown in FIG. 3.

A further important feature of the invention is the location of sliding pin 33 in the upper part of recess 32 as shown in FIG. 2. When one end of pin 33 strikes fixed part 48, the other end is caused to strike an upper part of gate 46 remote from concave area 58. This is shown in phantom in FIG. 6. Since pin 33 strikes this upper part of gate 46, a pivoting action by gate 46 takes place on curved surface 38, and the gate 46 is ejected in a pivotal manner from die plate 18 as indicated by the arrow 62 in FIG. 4.

The above description is a preferred embodiment of the subject novel die casting apparatus for forming and ejecting metal parts so that trimming is not necessary. Further modification is possible within the scope of the invention. For example, the die cast part may be formed with part in plate 20 and part in plate 16. In such case the draft angle would be different in the plates to insure that the die part would be retained in plate 20 upon the movement away from fixed plate 16. Corresponding modification would then be made in the through opening 26. It is also possible to change the shape of gate 46 as long as the smallest or pinhole point is retained at the end attached to the cast part and a concave portion is provided at the other end to provide for a retention within the movable plate and then for pivotal ejection.

it will be understood that still further changes and modifications may be made by those skilled in the art in the particular features of the apparatus and method which has been described above for illustrative purposes without departing from the scope of the invention as defined by the following claims.

What I claim is:

1. A method of degating and ejecting a metal cast part formed in a die comprising positioning a first outer die plate having a first recess therein so that it is in abutment with one side of a second inner die plate having an opening therethrough, said first recess being in alignment with said opening, said opening having a reduced cross section at the junction of said first recess that is less than the cross section of said first recess at said junction;

providing a third outer die plate having a second recess with an undercut edge portion;

positioning said second die plate so that its other side is in abutment with said third outer die plate and said second recess is in alignment with said openmg;

injecting molten metal into said opening and said recesses to thereby form a gate part in said opening and said second recess and to form the cast part in said first recess;

moving said third die plate away from said second die plate thereby separating said gate part from said cast part due to the reduced cross section of said opening at the junction with said first recess; then ejecting said gate part from said third outer die member by pivoting said gate part out of said second recess about said undercut edge portion; and

moving said first die plate away from said second die plate and ejecting said cast part therefrom after said first mentioned step of moving said third die plate.

2. A method according to claim 1 including holding said first and second die'plates stationary when said third die plate is moved away, and holding said second die plate stationary while said first die plate is moved away.

3. The method of claim 1 comprising forming said gate part in said opening in the form of a frustoconical part having its smaller diameter end at said junction.

4. The method of claim 1 comprising before said step of ejecting, positioning ejection means to slide into said second recess to contact said gate part at a point displaced on the opposite side of the center of the portion of said gate part in said second recess from said undercut edge portion, said step of ejecting comprising urging said ejection means against said gate part at said point to cause said gate part to pivot outwardly about said undercut edge portion as it is ejected. 

1. A method of degating and ejecting a metal cast part formed in a die comprising positioning a first outer die plate having a first recess therein so that it is in abutment with one side of a second inner die plate having an opening therethrough, said first recess being in alignment with said opening, said opening having a reduced cross section at the junction of said first recess that is less than the cross section of said first recess at said junction; providing a third outer die plate having a second recess with an undercut edge portion; positioning said second die plate so that its other side is in abutment with said third outer die plate and said second recess is in alignment with said opening; injecting molten metal into said opening and said recesses to thereby form a gate part in said opening and said second recess and to form the cast part in said first recess; moving said third die plate away from said second die plate thereby separating said gate part from said cast part due to the reduced cross section of said opening at the junction with said first recess; then ejecting said gate part from said third outer die member by pivoting said gate part out of said second recess about said undercut edge portion; and moving said first die plate away from said second die plate and ejecting said cast part therefrom after said first mentioned step of moving said third die plate.
 2. A method according to claim 1 including holding said first and second die plates stationary when said third die plate is moved away, and holding said second die plate stationary while said first die plate is moved away.
 3. The method of claim 1 comprising forming said gate part in said opening in the form of a frustoconical part having its smaller diameter end at said junction.
 4. The method of claim 1 comprising before said step of ejecting, positioning ejection means to slide into said second recess to contact said gate part at a point displaced on the opposite side of the center of the portion of said gate part in said second recess from said undercut edge portion, said step of ejecting comprising urging said ejection means against said gate part at said point to cause said gate part to pivot outwardly about said undercut edge portion as it is ejected. 